Orienting live well perforating technique provides innovative sand-controlmethod in the North Sea

The Varg field is a development in the North Sea operated first by Saga Pet roleum and currently by Norsk Hydro. It consists of a not-normally-manned w ellhead platform (WHP) with dry wellheads and a floating production storage offloading (FPSO) vessel for processing the crude. The reservoir is hetero geneous sandstone of Upper Jurassic age, with estimated reserves of approxi mately 35 million STB. During development planning of the field, it was felt that sand production was likely to occur, and this phenomenon was actually experienced during we ll testing. Because this development was considered to be a marginal field, an extensive program was initiated to review and select a technical comple tion solution that would minimize the risk of sand production so that produ ction potentials could be maximized. This paper discusses how a unique perf orating solution was developed to provide the controls needed to manage the potential for sand production. The first part of this paper summarizes (1) the drainage strategy, and the implications of that strategy on selecting the perforation intervals, and ( 2) the results of a rock mechanics study that focused on the conditions cri tical for the onset of sand production, as well as recommendations for mini mizing the risk. The primary recommendations were to avoid perforation of t he weakest intervals and to shoot perforations that would be oriented paral lel to the maximum horizontal stress. The second part of the paper describes how successful oriented perforating was achieved in these wells. The primary completion challenges included the following: Development of a slickline system that could perforate the entire zone simu ltaneously in a given direction in a vertical well. A means to remove the perforating guns from the well without having to kill it after completion of the perforation, as there was insufficient rathole to leave the guns in the hole. An oriented modular perforating system was developed so that these conditio ns could be achieved. The requirements were met by installing a gun anchor in the well before the completion was installed. Then, the orientation of a n orienting lug was measured with a gyro, and, based on the data from the s urvey, the guns were aligned in the correct orientation. Subsequently, gun sections of length maximized to available lubricator length were run on sli ckline. The gun section aligned itself automatically to the measured orient ation of the orienting lug because of the equipment design. Currently, thre e wells have been perforated using this system. All of them are sand-free s ince startup 11/2 years ago.